In recent digital cameras and mobile phones equipped with digital cameras, imaging devices have a larger number of pixels or recording pixels, and the display devices installed for checking photographed images have become smaller in size and larger in the number of pixels.
However, the number of pixels of a display device that is normally installed is not sufficient compared with the increase in the number of pixels in imaging devices (recording pixels).
Because of this, even after an image taken with a reproduction function is checked immediately after photographing, and focus is confirmed, a user is often disappointed at defocusing when the image is displayed on a large-sized monitor of a television receiver or a personal computer at home, or when the image is enlarged in size and is printed out with a printer, for example.
To counter this, there have been suggested techniques by which the state of a device such as a trace of camera shake or motion at the time of photographing is measured, and a warning is displayed to the photographer if the result of the photographing is likely to be adversely affected by such a state (see Patent Documents 1 through 3). These techniques have been put into practical use.